Social media and the stock market went wild, briefly, on Tuesday when this (hacked) Associated Press tweet appeared around 1 p.m.: "Breaking: Two Explosions in the White House and Barack Obama is injured."

The AP took down its Twitter account and quickly announced it had been hacked.

The FBI is investigating the incident, said bureau spokeswoman Jenny Shearer.

Rest assured, there was no attack on the White House ? and aides reported that President Obama was busy at work.

"The president is fine," spokesman Jay Carney said. "I was just with him."

A group of hackers loyal to embattledSyrian President Bashar al-Assad claimed responsibility for the hoax, tweeting out: "Ops! @AP get owned by Syrian Electronic Army! #SEA #Syria #ByeByeObama."

The Dow Jones industrial average plunged more than 128 points in seconds after the report. It recovered just as quickly when the report was found to be false.

The Securities and Exchange Commission declined to comment on the incident, as did the New York Stock Exchange.

The incident took place eight days after the Boston Marathon bombings.

In a statement, the Associated Press said, "The AP twitter account has been hacked. A tweet about an attack at the White House is false. We will advise on acct. status."

The AP confirmed that its Twitter account has been suspended, and "it was working to correct the issue."

(Note: This tweet drew instant suspicion from journalists. The Associated Press style is to never refer to "Barack Obama." It is always "President Barack Obama." The service also normally capitalizes the word "BREAKING" when news happens.)

The wire service said its mobile Twitter account was also broken into, and all of its accounts have been shut down.